91 octane vs e85 in flex fuel Tahoe/suburban?

iboughtatahoe23 said:

So you’re running e85 year round even in sub zero temps? It gets VERY cold here in NESD

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Yes. Gets pretty cold here, too, and that's when I drive the Hoe the most 'cause 4x4. And I'm at least 4000 ft higher; you can't be more than 2k' in elevation, are you?

iboughtatahoe23 said:

I hear good things about chevron with Techron

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Chevron with Techron has actually lowered its concentration of poly ether amines lately, but at least it still has PEA in it.
Don't fear the other stuff, they all come highly recommended from the folks at Bob Is The Oil Guy, plenty of PEA.

petethepug said:

Get the (e85) conversion kit.

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iboughtatahoe23 said:

My Tahoe is flex fuel.

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Sorry, was referring to @B-train 08 YXL Denali

In my Wifes 2015 Tahoe Flex fuel What I have learned is E85 is not good in a sitting tank or system. It will condensate quickly and then will rust a sitting system. We run it if the tahoe is always being used. The overnight and cold weather start ups and the smell you get is the condensate cleaning out your system. Most throttle and injector cleaners are 80% water. And yes e85 does run cleaner than most 87 and 91 octane fuels.
The sad truth about those octanes is they are actually a blend of things, that blend is constantly being changed in the USA, especially from summer to winter, then maker to maker. The TV show, Engine Masters tested different octanes on a dyno to see about performance and found almost No difference between 87 and 91 octanes. Check it out, its interesting for us gearheads.
I have a 2010 Silverado that has a dod/ vvt delete, mild cam, shorty headers and HP tuners tune. It is a flex fuel LMG gen 4 LS. Due to my tune I cant use E85. Id need some additional parts and sensors to run it. I also dont bother with 91 octane. Its a daily driver truck that runs 87 octane and keep it in Tow Haul mode most of the time. And Yes, sadly because I do haul a trailer often I had to write 2 tunes for this one truck.

E85 (E??, who actually knows what the actual ethanol is) is NOT FOR STORAGE.
Unless I can use it all up in 4 days or less, I avoid E85.

MD-Wood said:

Due to my tune I cant use E85. Id need some additional parts and sensors to run it. I also dont bother with 91 octane.
Its a daily driver truck that runs 87 octane and keep it in Tow Haul mode most of the time.
And Yes, sadly because I do haul a trailer often I had to write 2 tunes for this one truck.

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Your first two tunes can't use E85, true, and I certainly don't recommend E51 for the winter, but
you've already written two tunes, you COULD write an E85 only tune (not necessarily saying you should) ...

I thought I'd share information from a Sunoco fuel representative that would seem to only be relevant in this discussion if the vehicle sits for long periods.
Higher octane fuel has longer shelf life because of the additives used in the higher octane fuels.
It applies to our garage where any number of gas driven things sit the winter out.

EddieC said:

I thought I'd share information from a Sunoco fuel representative that would seem to only be relevant if the vehicle sits for long periods.
Higher octane fuel has longer shelf life because of the additives used in the higher octane fuels.

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Look for stations with Top Tier fuel.

iboughtatahoe23 said:

Which of these is better? I wanna save money of course but if 91 octane overall will increase longevity of the vehicle than by all means

Idk if it matters but the winters are harsh and the summers are hot here.

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I would use 91 octane.

If you drive GENTLY enough to make passengers wonder why you drive so gently,
87 octane should not be an issue.
That said, if you work or play hard with your engine, 91 or 93 octane.

MD-Wood said:

In my Wifes 2015 Tahoe Flex fuel What I have learned is E85 is not good in a sitting tank or system. It will condensate quickly and then will rust a sitting system. We run it if the tahoe is always being used. The overnight and cold weather start ups and the smell you get is the condensate cleaning out your system.

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I've pumped about 1,800 gallons or more of ethanol in my truck over the years. Many times the 1/4 tank of fuel sat for a month in the tank before the truck was refueled, often with another tank of ethanol. We've experienced no fuel system problems. Truck is at about 207K miles on her original injectors/fuel pump. We don't really have any metal in our fuel systems anymore. Do we?

Here in Florida, our E85 is about the same alcohol content year round. Or rather, my car calculates it to between 72 and 80 percent.

So, when it's cold out, in the 50s or lower, the truck stalls on the first remote start in the morning. I take it that the E85 in the lines is really cold and doesn't want to fire. She always fires right up on the second press of the button.

Looking forward to running it again but want to make the first 1/4 mile passes on gasoline as that's what my last passes were on. Soon.